Vehicle suspension systems are designed to absorb or isolate the passenger-carrying body of the vehicle from road shocks arising from irregularities in the road and to provide continuous contact between the wheels of the vehicle and the road in order to maximize passenger comfort, safety and road handling.
Passive suspension systems consisting of mechanical springs and dampers often fail to meet the above objectives due to the tendency of mechanical springs being either too hard or too soft resulting in insufficient or excessive movement of the passenger-carrying compartment respectively in response to road shocks. Passive suspension systems also cannot produce active forces rapidly to absorb road shocks and therefore undesirable pitch and roll motions of the passenger-carrying compartment cannot be properly suppressed.
Active suspension systems, which typically comprise hydraulic or electromagnetic actuators, provide improved performance over passive suspension systems but still exhibit deficiencies of their own. Hydraulic active suspension systems for instance include an array of components such as electric controllers, oil/air pumps and oil/air tanks forming relatively complex structures which must be carefully assembled and calibrated to operate properly. Accordingly, the production time and costs are relatively high. Furthermore, hydraulic systems tend to have low dynamic response and low reliability due to oil/air leakage and other faults which necessitate regular ongoing maintenance.
Electromagnetic active suspension systems based on permanent-magnet actuators suffer from similar problems as those of hydraulic type systems in terms of the complexity of their structures and components which exacerbates production costs. Additionally, the reliability in performance of existing electromagnetic active suspension systems is adversely affected by the tendency of the permanent magnets to demagnetise over time.
The above-described deficiencies in existing suspension systems compromises passenger ride comfort and safety and there is a perceived need to address such problems.